On a recent episode of The Middle, America’s favorite geekette, Sue, set out to prove that smiling was contagious. Unfortunately, despite her sparkling enthusiasm, she didn’t quite get the response she wanted. But, ever the optimist, Sue still believes that smiling is contagious. And she’s right!

In a Swedish “smile study,” volunteers looked at pictures of different facial expressions while trying to control their own reactions. But when asked to meet a smile with a frown, they simply couldn’t stifle their grins. Apparently, seeing a smile triggers an unconscious reaction in the brain and then your face can’t help but join the party!

Want to make someone feel special, especially on their birthdays? Always start with a smile. And if you can’t do it in person, send one in a card.